Referring to FIG. 1, an existing envelope making plate includes a plate body 1′ with a marking groove 11′, a reference edge 13′ abutting against or aligning to an envelope paper 2′, a scale line 14′ or an indication line which is direct to the type of the envelope. A utility knife is used to mark a folding line 21′ on the envelope paper 2′ along the marking groove 11′. The envelope is folded by means of the folding line 21′. The zero point 18′ on the scale line is the projection point of the intersection of the adjacent folding lines which is vertically projected to the reference edge. When making an envelope, the envelope paper 2′ abuts against or aligns to the reference edge 13′ and then aligns to the scale line or the indication line according to the size of the envelope. A first folding line 21′ is marked under the constraint of the marking groove 11′. Then the envelope paper is rotated 90 degrees and aligns to the reference edge 13′ again. The first folding line is aligned to the second indication line 12′ and a second folding line is marked. The above operation is repeated until all the folding lines are marked.
The disadvantage of the existing envelope making plate is that, the angle between the marking groove 11′ and the scale line 14′ is set as an obtuse angle of 135 degrees, which makes the breadth of the plate body larger and the flat space of the plate body can't be fully utilized. Meanwhile, because the plate body is larger, the rigidity and intensity of the plate body are insufficient. A reinforcing rib is added on the back of the plate body to make sure the front of the plate body can work normally, thus the use of the space on the back of plate body has to be abandoned.